The present invention relates to a transporting device which has wheels and a stair climbing unit Which is driven by an electric motor and provided with climbing legs.
Transporting devices with step climbing units are known in many modifications. One of such transporting devices is disclosed in German patent document DE 37 13 564, and used in particular for a wheelchair. It is provided on both sides with a wheel pair whose wheels are turnable around special, jointly driven spaced parallel shafts. The shafts are connected each eccentrically with a hub disc, on which a rim of associated wheel is concentrically and rotatably supported.
The German patent document DE 197 45 153 discloses another transporting device which has wheels arranged on a frame and a stair climbing unit driven by an electric motor. The electric motor drives first eccentric lever, on which correspondingly a second eccentric lever is rotatably transported. It is rotatably supported with its end on supports which are linearly guided on the transporting device. Toothed gears or chains are arranged between the first and second eccentric levers. These transporting devices have a common feature that they require a relatively expensive construction with the use of chains or toothed gears. Moreover, a relatively great electric motor for the stair climbing unit is needed.
Accordingly, it is an object of present invention to provide a transporting device of the above mentioned general type, which eliminates the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a transporting device in which the electric motor drives a drive shaft which is formed as a crankshaft symmetrical to the central longitudinal axis of the device, and on each half of the drive shaft on a crank climbing leg and on a further crank a wheel is rotatably supported.
Since the drive shaft formed at a crankshaft moves up and down both the climbing legs and the wheels, an expensive power transmission by means of chains or gears is dispensed with. The stair climbing unit can be produced in a price-favorable manner and also not susceptible to disturbances. A further advantage of the transporting device when compared with the German document DE 37 13 564 is that the climbing legs take up the load with smaller distances before the next stage. Thereby the horizontal extension between the supporting leg and the wheel set on the next step is shortened. The loading change at the hand grips is therefore substantially reduced.
The cranks for lifting and lowering of the wheels can enclose for example an angle of substantially 180xc2x0 with the cranks for lifting and lowering of the climbing legs. When both the wheel cranks and the climbing leg cranks have the same length, the required torque and the motor power is minimal. When compared with the transporting device disclosed in German patent document DE 197 45 153, the required torque and the motor power is half as high. Finally, the transmission and the accumulator can be dimensioned correspondingly smaller. Thereby the weight or the total transporting device is reduced. Moreover, the accumulator can have a lower power and a shorter charging cycle.
For guiding the climbing legs on the device, they can be raisable lowerable, preferably along the guiding rails. Furthermore, for reducing the friction between the climbing legs and the guiding rails, the climbing legs can be guided preferably with guide rollers along the guiding rails.
Alternatively to a guidance on a rail, the climbing legs can be guided for example also by a guiding crank supported on a frame for lifting and lowering movements. This guiding crank which is arranged not on the crank shaft rotates parallel to the climbing leg cranks.
The guiding cranks and the cranks for lifting and loading movement of the climbing legs can be connected with one another by a chain or a transmission band. Thereby it is prevented that the guiding cranks and the climbing leg cranks are in an unstable position, when the guiding cranks and the climbing leg cranks are oriented in one line.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.